Breast Density May Be Top Indicator of Cancer Risk

Women whose breasts are predominantly made up of more dense, glandular tissue face higher odds for breast cancer, a new study finds.

The researchers added that, based on their study of 200,000 women, breast density may be the most important gauge of breast cancer risk, eclipsing family history of the disease and other risk factors.

Overweight or obese women typically “have lower breast density, though age is a strong determinant of breast density as well,” study first author Natalie Engmann, a Ph.D. candidate in UCSF’s department of epidemiology and biostatistics, said in a university news release.

Denser breasts have been thought to be more prone to tumors because of cellular factors, and also because smaller tumors in dense tissue are tougher to pick up on mammograms. The new study sought to quantify the risk.

While gaining excess weight can lower tissue density, obesity has been implicated in many diseases, including breast cancer, in postmenopausal women.

On the other hand, “tamoxifen is the only medication that can decrease breast density,” she said, but, “like much of medicine, the risks must be weighed against the benefits.” Some of those risks include a higher chance of developing uterine cancer or deep vein thrombosis, which are blood clots in the legs